As punts go, it has been a costly one. The weekend's news that the US Congress has passed laws curbing payments for internet gambling is much more than the old roulette call of "no more bets". Investors' chips have effectively been dragged off the table and they must now slope off home and justify further losses - to add to the ones already incurred when this saga gathered speed earlier this summer.

While most investors will have known they were playing with a potentially loaded deck by backing gaming companies actively touting for American punters, few predicted just how suddenly the baize would have been pulled from underneath them. A basket of 30 publicly-listed online gambling shares compiled by financial website ADVFN shows that their combined value has plummeted by £5.3bn since the arrest in America in July of BetonSports chief executive David Carruthers.

"I'm not going to gloat, but my partner Eric Semel, whose father runs Yahoo!, has been saying this for years," observes Peter Dubens, the chairman of UkBetting, an online gaming group that shuns the US as well as developing sports content websites. "We erred on the side of caution. Now the content side of our business is a lot more valuable than before the weekend."

He may or may not be right, but just like in a real casino there will be winners and losers as this latest game plays itself out. While it is tempting to assume that all the losers will be the US-facing sites, it may not be as simple as that as different companies are playing with different sized chip stacks. UkBetting, for example, had cash of £13m at the end of June, while at the same time PartyGaming had £70m, albeit when 77pc of revenues came from the US. Now it predictably talks about how quickly its non-US business is growing.

That is now the goal for all sites that previously focused on America and this could mean even more advertising and promotion. Formerly US-facing sites are bound to up the ante in the battle for customers in Europe, Latin America and Asia.

Meanwhile, online punters tend not to be high rollers. They also spend less when they are not American. Sportingbet's US sports clients on average wager £27 per bet. In Europe the figure is £13.

"I'm very clear what we have to do," says John Anderson, chief executive of 888 Holdings, which derives about half its revenues and profits from America. "This is a big loss, but I'm committed to getting back what we've lost from America. We've been very good at marketing." He insists that his company's sponsorship of Middlesbrough football club will not be affected by a shrinking customer base, but acknowledges that consolidation within the sector is almost inevitable.

Sources close to Ladbrokes, a company that has always declined US business but was actively reviewing that stance before this year's events overtook it, indicate that the company would "look at everything and see what is good value," although it does not currently have a shopping list of potential acquisitions.

One of the big draws of the top online poker sites is liquidity, but with the major market suddenly disappearing there will obviously be fewer people at the tables and - presumably - smaller prizes. Mergers solve that problem, almost immediately.

"Prize pools are one of the things that need to be addressed," admits John Shepherd, director of corporate communications at PartyGaming, "But people are there for a reason. They enjoy it."

Still, if some things remain in the air, nobody within the industry can claim they weren't warned. The flotation prospectuses highlighted the risks, while as far back as 2001, Sportingbet was hit by a lawsuit, filed by New Jersey, claiming the company had accepted illegal wagers from America. The action named the website along with its founder and chief executive and stated that the company could face a fine of £5,200 for each allegedly illegal bet taken.

In the end the action fizzled out, but it was a warning that turned out to be more than a bluff and leaves those within the industry wrestling with a dilemma. Do they cut and run or ignore one of gambling's great maxims? Never chase your losses.